What’s black & white and red, blue and green all over? Tanagers!
Recently published research shows that in tanagers and other songbirds, the bright colors we see are enhanced by hidden black and white feathers located to maximize visual impact.
Birds have many kinds of feathers which evolved to meet a variety of needs, including keeping an individual warm and dry, allowing flight, offering camouflage, and communicating breeding readiness or fitness. Contour feathers cover a bird’s body which show the characteristic bright colors or muted tones that we use to identify each species.
The study found that male tanagers' external contour feathers are paired with achromatic (black or white) feathers which enhance the colors we see. The carotenoid-pigmented red and yellow feathers are paired with a hidden white layer, while structurally-colored blue and violet feathers are paired with a hidden black layer. Results for females were different and the authors suggest that less colorful females may be the result of these differences in the achromatic layers.